Okay, now before I start, let me say this: MGS fanatics, walk away. Now. What I have to say will make you very upset.
I have played several of the Metal Gear games from the NES up until today. Beaten most of the ones that I've played except for the original MGS. It isn't that I don't care for the graphics so much as the gameplay is a little too overly convoluted and, like every game in the MGS series, far too much value on story. And Metal Gear Solid 4: Guns of the Patriots is no different.
Visually, it's stunning in many details, although I notice frequent framerate drops, and many of the stealth actions of the previous games are...dumbed down. Not to mention that the whole sneak-through-a-base thing is more or less paid lip service and the key-anditem-hunting game that actually helped make the series enjoyable is gone (mind you, I haven't played Snake Eater yet), and instead feels more like a fratboy actioner with firepower on demand.
However, the game is a lot of fun, when you're playing it. When you're not playing it, it's because you're watching a 20-30 minute cutscene depicting cool stuff that you aren't actually doing (well...for the mostpart...won't spoil the one cool thing you do actually get to do). Many of the boss fights are by the numbers - mostly because it's little different than any other MGS game.
Now, luckily, you can skip the cutscenes, but then you don't know what the hell is going on. And if you don't have time to screw around, you miss the whole point of Kojima's alleged masterpiece (and yet I've read Tom Clancy books more complex).
The shooting is rock solid, although I found the stealth left much to be desired. While the weapons on demand was a pretty cool feature, it felt unnecessary, especially when a lot of the guns essentially did the same thing and it was more or less a matter of picking your favourite model.
I think that the idea of aging Snake was pointless. I realise that it is supposed to add another dimension of depth, but it really didn't. The stamina bar and how it was used, however, did. It certainly helped increase the tension in a boss fight or two.
As far as level design goes, all of the stereotypical locales are there, plus a nod to past games. This really did not impress me, although it may be because I've read and experienced too many modern-day techno-thrillers. However, desert, jungle, tundra...it kinda sounds like a Ghost Recon game.
In short, as a storytelling vehicle, Metal Gear Solid 4 is a great fan service, but a slap in the face to the average gamer. It is artificially lengthened by way of semi-interactive cutscenes that rarely progress the story so much as try to make characters look cool and throw in what seem to be contrived emotional bonds (e.g. token romance side-storylines). This adds a level of superficiality that really denegrates the game as a game. I realise some people might view it as art...but if it is, it's little more than David with a dress and cockring. As offensive as that sounds, the whole point is that it's dressed up for the sake of dressing it up; underneath, it's still the Statue of David, and it doesn't need those things - especially when they're gaudy and unnecessary. i.e., the game underneath is excellent, you just have to remove the fluffy excrement piled on top by a misguided director. At least he was kind enough to give you the tools to get around them.
So, I sincerely hope that the next Metal Gear game incorporates story that you can read instead of needing to extrapolate it from deliberately paced cutscenes. It needs to be told more efficiently, or at the least, the resources need to be on hand in an efficient manner in the game. Because if I play MGS4 again, I'll be skipping those cutscenes; they're just too long for people with lives.